1. Field of the Invention
The present invention relates to a color image forming device which forms a multi-color image by use of an electrophotography technique.
2. Description of the Related Art
Conventionally, there are known several color image forming devices of a type that forms multi-color images by use of an electrophotography technique: for example, as disclosed in Japanese Patent Examined Publication No. Hei 3-18182, a color image forming device which forms color toner images by colors one by one sequentially on a light conductive photosensitive member and transfers the color toner images onto recording paper or the like; as disclosed in Japanese Patent Unexamined Publication No. 2-302768, a color image forming device which forms a one-color toner image on a light conductive photosensitive member and transfers the one-color toner image onto recording paper or the like, and the process of formation and transfer of the one-color toner image is repeated to thereby form multi-color images; and, as disclosed in U.S. Pat. No. 4,078,929 or in Japanese Patent Unexamined Publication No. 55-83070, color image forming devices each of which forms two-color toner images on a light conductive photosensitive member and then transfers the two-color toner images onto recording paper or the like.
In the first and second color image forming methods employed in the above-mentioned conventional color image forming devices, since the toner image forming step must be repeated a number of times corresponding to the number of colors of the toner, it takes much time to obtain a final color print.
In the third conventional color image forming method, since two kinds of electric charge latent images (three-value latent images) are formed at a time on the light conductive photosensitive member and they are developed by use of two kinds of color toners, the time necessary for forming images can be reduced. When there is used, as the photosensitive member, an organic light conductive photosensitive member or an As.sub.2 Se.sub.3 photosensitive member which takes 0.2 to 1 sec. as the time (the light response time) in which the electric charge after exposure of the light image is attenuated, there has been a limit to increase in the image forming speed and to reduction of the size of the image forming device. Also, since the respective toner images are not superimposed on one another, the color reproduction range of the composite color is narrowed. Further, because the two kinds of latent images are sequentially developed with two kinds of developers, when the latent images are developed by the second developer, the toner image developed by the first developer can be possibly shaved off. And, in the second development, it is difficult to obtain a sufficient image density. These make it difficult to obtain a multi-color image of high quality.